Without living in the US it is hard for you to come up with a valid argument against prioritizing automobile infrastructure.
Population density alone makes it an issue outside of large cities like New York, because of that you'll also find most cities have pretty lackluster public transportation.
It is tragic that people are hurt and worse because of automobiles but they are a fact of life in America and cyclists are a very minor subset of the population for which taxes rarely cater.
One of the major problems with bicycling is the lack of respect between the cyclist and the motorist, it goes both ways but there are plenty of motorists who do not understand the laws and despise cyclists. But there are also many cyclists who fail to follow the laws which helps perpetuate the hate from motorists.
If more cities had the budget for dedicated cycling paths and road usage I'm sure they would use it but as it is now only some "greener" cities are able to do anything.